Do you know the name of the actual photographer who took the pics - wonder if he may have more sway ? Definitely get a copy of all the 6*4's before doing anything though. They probably think that is sufficient a gesture - mean b-st-ds.
It doesn't make good business sense let alone show compassion. If they just keep them on file rather than offer to sell you a copy CD then you don't buy anything more so they are going to lose out financially and risk their reputation. Even if they let you have a copy now, you might still go back to them for some mounted ones as and when you can afford it.